Foxp3 Expression and Nitric Oxide Production in Peripheral Blood Mononuclear Cells of Communicants with Pulmonary Tuberculosis

The understanding of the mechanisms involved in the immune response is of significant relevance to the control of tuberculosis ( TB ), especially in individuals living with patients with TB . To characterize the nitric oxide ( NO ) production and the F oxp3 marker expression in this population, peripheral blood mononuclear cells of intradomiciliary contacts of individuals with pulmonary tuberculosis with ( CT b, susceptible) and without ( ST b, resistant) previous history of active infection were stimulated in vitro with M ycobacterium tuberculosis antigen (TbAg) and with the mitogen C oncanavalin A for 24 and 48 h. The groups analysed did not present significant difference in the Foxp3 mRNA expression nor in the NO production. Negative correlation ( P  = 0.09) between NO and Foxp3 after a 48‐h stimulation with TbAg was observed in the STb group. In this group, after a 24‐h culture stimulated with TbAg ( P  = 0.03), this same correlation was observed. In comparison with the cytokines previously studied by our group (Cavalcanti et al ., 2009), a positive correlation was observed between IL‐10 and Foxp3 after a 48‐h culture of cells from communicants susceptible to tuberculosis (STb) stimulated with TbAg ( P  = 0.04). Evaluating the entire population, a positive correlation was observed between the cytokine TNF‐α and the Foxp3 marker in the cultures stimulated for 24 ( P  = 0.03) and 48 ( P  = 0.02) hours with TbAg. Therefore, considering the similarity in the exposure and the individual capacity of responding to the contact with M . tuberculosis , the present study contributes to the comprehension of the immune regulation in individuals living with patients with TB .